diff --git a/ChangeLog b/ChangeLog
index 9da88d05ac..e44fedde61 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+Sat Jun 23 23:19:31 2012  Tanaka Akira  <akr@fsij.org>
+
+	* internal.h (rb_execarg): add new_pgroup_given and new_pgroup_flag
+	  fields.
+
+	* process.c (EXEC_OPTION_NEW_PGROUP): removed.
+	  (proc_spawn_cmd): take a struct rb_execarg argument.
+	  use the new fields.
+	  (rb_execarg_addopt): use the new fields.
+	  (rb_spawn_process): follow the proc_spawn_cmd change.
+	  
 Sat Jun 23 20:26:36 2012  Tanaka Akira  <akr@fsij.org>
 
 	* internal.h (rb_execarg): add fd_dup2, fd_close, fd_open,
diff --git a/internal.h b/internal.h
index 674525daf0..cbcfe4ecf2 100644
--- a/internal.h
+++ b/internal.h
@@ -183,6 +183,8 @@ struct rb_execarg {
     unsigned close_others_given : 1;
     unsigned close_others_do : 1;
     unsigned chdir_given : 1;
+    unsigned new_pgroup_given : 1;
+    unsigned new_pgroup_flag : 1;
     pid_t pgroup_pgid; /* asis(-1), new pgroup(0), specified pgroup (0<V). */
     VALUE rlimit_limits; /* Qfalse or [[rtype, softlim, hardlim], ...] */
     mode_t umask_mask;
diff --git a/process.c b/process.c
index 80d32dbd26..b30e413b28 100644
--- a/process.c
+++ b/process.c
@@ -1253,10 +1253,6 @@ rb_proc_exec(const char *str)
     return ret;
 }
 
-enum {
-    EXEC_OPTION_NEW_PGROUP
-};
-
 static void
 mark_exec_arg(void *ptr)
 {
@@ -1345,14 +1341,15 @@ proc_spawn_cmd_internal(char **argv, char *prog)
 #endif
 
 static rb_pid_t
-proc_spawn_cmd(char **argv, VALUE prog, VALUE options)
+proc_spawn_cmd(char **argv, VALUE prog, struct rb_execarg *eargp)
 {
+    VALUE options = eargp->options;
     rb_pid_t pid = -1;
 
     if (argv[0]) {
 #if defined(_WIN32)
 	DWORD flags = 0;
-	if (RTEST(rb_ary_entry(options, EXEC_OPTION_NEW_PGROUP))) {
+	if (eargp->new_pgroup_given && eargp->new_pgroup_flag) {
 	    flags = CREATE_NEW_PROCESS_GROUP;
 	}
 	pid = rb_w32_aspawn_flags(P_NOWAIT, prog ? RSTRING_PTR(prog) : 0, argv, flags);
@@ -1579,11 +1576,11 @@ rb_execarg_addopt(VALUE execarg_obj, VALUE key, VALUE val)
 #endif
 #ifdef _WIN32
         if (id == rb_intern("new_pgroup")) {
-            if (!NIL_P(rb_ary_entry(options, EXEC_OPTION_NEW_PGROUP))) {
+            if (eargp->new_pgroup_given) {
                 rb_raise(rb_eArgError, "new_pgroup option specified twice");
             }
-            val = RTEST(val) ? Qtrue : Qfalse;
-            rb_ary_store(options, EXEC_OPTION_NEW_PGROUP, val);
+            eargp->new_pgroup_given = 1;
+            eargp->new_pgroup_flag = RTEST(val) ? 1 : 0;
         }
         else
 #endif
@@ -3525,7 +3522,7 @@ rb_spawn_process(struct rb_execarg *eargp, char *errmsg, size_t errmsg_buflen)
     }
     else {
         char **argv = ARGVSTR2ARGV(eargp->invoke.cmd.argv_str);
-	pid = proc_spawn_cmd(argv, prog, eargp->options);
+	pid = proc_spawn_cmd(argv, prog, eargp);
     }
 #  if defined(_WIN32)
     if (pid == -1)